Determination of nucleation and growth mechanisms of the crystallization of amorphous alloys; application to calorimetric data

An analytical phase transformation model has been used to study the kinetics of crystallization of amorphous alloys subjected to either isothermal or isochronal anneals. The model has been applied to Pd₄₀Cu ₃₀P₂₀Ni₁₀ and Mg_82.3Cu _17.7, employing isothermal and isochronal differential scanning calorimetry. The analytical model comprises different combinations of various nucleation and growth mechanisms for a single transformation. Applying different combinations of nucleation and growth mechanisms to the same experiments, the nucleation and growth modes dominating the crystallization and the values for the corresponding kinetic parameters including the constant activation energies for nucleation and growth, have been determined. Further, the influence of isothermal pre-annealing on subsequent isothermal or isochronal crystallization kinetics, involving a gradual change of nucleation mode up to site saturation with increase of pre-annealing, can be analyzed.